Elbio Dagotto, University of Tennessee, Knoxville

"Surprises in electronic correlated systems: block and spiral spin states, Majoranas, and pairing"

Abstract: Recent results in the area of many-body theoretical physics will be informally discussed. Employing computational techniques, I will address several surprising states that emerge in regions of parameters space with competing tendencies. I will mainly use low dimensional multi-orbital models for chains and ladders, but results in two dimensions will also be shown. The computer revealed a variety of exotic phases difficult to anticipate. These new states involve spin staggered arrangements of ferromagnetic blocks [1], as well as spirals that become the ground state at intermediate range couplings [2].

Coupling by proximity those spirals to a BCS s-wave superconductor, induces in the spiral both a singlet and triplet pairing components and we found Majorana zero modes at the spiral’s chain edges [3]. In two dimensions, a “skyrmion crystal” [4] can also be a platform for Majoranas [5].

Finally, time allowing, I will move into novel superconductors and discuss: (i) A two-orbital Hubbard model [6,7] generalization of the S=1 Haldane chains. This fermionic model is predicted to develop superconductivity upon hole doping [8]; (ii) Our recent results [9] in the fast growing area of the recently discovered high-Tc superconductivity in La3Ni2O7 at high pressure, with predictions of pairing and magnetic order channels.

Work supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division.

[1] See for example J. Herbrych et al., Nat. Comm. 9, 3736 (2018); N. Patel et al, Commun. Phys. 2, 64 (2019); J. Herbrych et al. PRB 102, 115134 (2020); M. Sroda et al., PRB 104, 045128 (2021), and references therein.
[2] J. Herbrych et al, PNAS 117, 16226 (2020).
[3] J. Herbrych et al, Nat. Comm. 12, 2955 (2021).
[4] N. Mohanta et al., Phys. Rev. B 100, 064429 (2019), and references therein. See also N. Mohanta et al., Com. Phys. (Nature) 3, 229 (2020).
[5] N. Mohanta et al., Com. Phys. (Nature) 4, 163 (2021); npj Quantum Materials 7, 76 (2022).
[6] N. D. Patel et al., npj Quantum Mater. 5, 27 (2020).
[7] A. Jazdzewska et al., arXiv: 2304.11154.
[8] P. Laurell et al., in preparation.
[9] Y. Yang et al., arXiv:2306.03231, 2307.15276, 2308.07386.